Noisy spinning shaft while sailing

[wstockho]

I have a Hunter 33 with a Yanmar 2GM20F diesel and a fixed 3-blade prop. I normally let the shaft free wheel while sailing in accordance with Yanmar's advice. Until lately, the spinning noise has been minimal, but sailing yesterday, the noise appeared much louder as if something is striking the shaft every revolution. I examined the shaft and the gears and everything appears normal from inside the boat. However, while sailing a few weeks ago I had a pretty significant shaft seal leak, so I tightened the packing gland nut 1/4 turn as recommended in the Hunter manual. This stopped the leak, but I have not noticed any shaft seal leakage since (none - no drips). I'm not sure if this is related to the noise problem. I'm planning to have divers examine the shaft and prop to see if there is anything that might account for the noise. I'd like to avoid a haul out if I can for obvious reasons. Any suggestions?

 

[quadrille38]

Probably now what you want to hear and doesn't solve your why now question but I replaced my fixed 3 blade with a feathering Maxprop. No more whirling noise, better backing and stopping, and better forward motoring. Highly recommend it.

 

[uncledom]

I don't think your supposed to tighten the gland nut to the point of "no leak". I believe there should be a drop or two of water per minute with the engine in gear, shaft turning, to ensure no air lock on the seal.

 

[John T1594]

Loose zincs?

I had a similar noise problem one season and it turned out that one of my shaft zincs had come loose, slid down the shaft and was knocking into the shaft strut.

 

[wstockho]

I had a similar noise problem one season and it turned out that one of my shaft zincs had come loose, slid down the shaft and was knocking into the shaft strut.

This was one of the possibilities I thought about. Divers coming this week to check.

 

[wstockho]

I don't think your supposed to tighten the gland nut to the point of "no leak". I believe there should be a drop or two of water per minute with the engine in gear, shaft turning, to ensure no air lock on the seal.

Agree, but the manual said to tighten 1/4 turn. When that was done, there was no leakage. I'm reluctant to back off the gland nut, but maybe that would be the best thing to do.

 

[wstockho]

Probably now what you want to hear and doesn't solve your why now question but I replaced my fixed 3 blade with a feathering Maxprop. No more whirling noise, better backing and stopping, and better forward motoring. Highly recommend it.

Good idea. I'll probably do this eventually.

 

[luv2sail67]

Change out prop

Good idea. I'll probably do this eventually.

We switched to a 3 blade vari-prop this season on our 38. Best investment so far on the boat! We gained .8 knots of boat speed at our normal cruising RPM and backing is now significantly better.